A cooling fan is a heat dissipation unit having good heat dissipation efficiency and being highly flexibly usable with other heat dissipation elements, and is therefore widely used at different places that require heat removal, including but not limited to traffic means, electric appliances, air-conditioning apparatuses and so on.
A cooling fan includes a rotor and a stator. The rotor is driven by electromagnetic induction to rotate relative to the stator. When the rotor rotates, blades thereon rotate at the same time to forcedly guide in and out airflow to dissipate heat. There are several types of fans, including axial-flow fans, cross-flow fans and centrifugal fans. Among others, the axial-flow fans are most frequently used with existing electronic devices for forcedly dissipating the heat produced by individual heat-producing elements and other electronic elements of the electronic devices. The cooling fans will inevitably produce vibration during operation to thereby adversely affect the operation of some precision electronic units, such as the hard disk drive, in the electronic devices. While all types of cooling fans will produce vibration during operation, such vibration is not allowed in some specific working environment, such as in servers. Therefore, it is very important to eliminate the occurrence of vibration during fan operation.